B. The surface of a silver cup turns black when it is exposed to air.
Answer;
-(3) an atom in an excited state
Explanation;
-An electron in a sodium atom gains enough energy to move from the second shell to the third shell. The sodium atom becomes an atom in an excited state.
-Ground state is the lowest allowable energy state of an atom. When electrons are subjected to stimuli like heat, light or electricity an electron may jump to a higher energy level, which is the excited state. Excitation is the elevation in energy level above the baseline energy state.
Periodic table<span> of the </span>elements, in chemistry, the organized<span> array of all the chemical </span>elements<span> in order of increasing atomic number—i.e., the total number of protons in the atomic nucleus.</span>
